Current regulating device



May 5, 1931. w. L. BOND 1,804,243

CURRENT REGULATING DEVICE Filed July 20, 1928 InvenTor' William L. Bond,

Hi5 ATTOr'ne Patented May 5, 1931 UNITED STATES PATENT OFFICE wnmnn I.BOND, OI SCHINECTADY, YORK, ASSIGNOB TO GENERAL ELECTRIC OOHPANY, ACORPORATION OF NEW YORK CURRENT nmum'rme DEVICE Application am Jul so,

My invention relates to current regulating devices, more particularly tovariable resistance devices such as rheostats and potentiometers, andhas for its object the provislon of a current regulating device having avaryingresistance per linear unlt whereby a tapered or non-uniformcurrent control may be obtained.

My invention has particular application to rheostats and otentiometerssuch as are used in radio receivers wherein the resistance element orconductor is in an annular form and the resistance is increased ordecreased by means of an angularly movable contact arm.

In general, the sound output from a radio receiver is controlled bymeans of a variable resistance in some part of the circuit, and thewell-known wire wound rheostat is often employed. A disadvantage ofthe-ordinary wire wound rheostat is that such a rheostat does not allowa control of sound volume which is uniform throughout the range of therheostat. This is due to the fact that the resistance of the rheostat isordinarily a linear to function of the angle of movement of the contactarm, whereas the sound output is not always a linear function of theresistance. It is therefore desirable to use a rheostat, the

resistance variation of which is other than a linear function of themovement of the contact arm so that the variation in sound volume may besubstantially proportional to the movement of the contact arm.

In carrying out In invention I have provided a current regu ating deviceutilizing a pluralit of resistance elements having different egrees ofresistance per linear unit, the resistance elements being held inoverlapping, parallel, electrically contacting relation.

For a more complete understanding of my invention reference may be hadto the accompanying drawing in which Fig. l is a rear elevation of arheostat embodying my invention; Fig. 2 is a side elevation in sectiontaken along the lines 22 of Fig. 1 looking in the direction of thearrows, and Fig. 3 is a perspective view showing the parts of therheostat in detached, unassembled relation.

Referring to the drawing, in carrying out me. Serial 1%. 294,251,

my invention in one form I have provided a rheostat comprising a basemember 10, on which is secured a high resistance element or conductor11, having a substantially constant resistance per linear unit, and alow resistance element or conductor 12 in overlapping, contactingrelation with a portion of the high resistance element for varying theeffective resistance per linear unit thereof. It is preferred that thebase member 10 be made of porcelain although any other suitableinsulating material may be used. An operating sha t 13 passes throughthe base member 10 at approximately the center thereof, and to one endof the shaft 13 is attached a movable contact arm 14. Contact terminals15, 16 and 17 are provided, being connected respectively to the ends ofthe high resistance element 11 and to the contact arm 14. The basemember 10 is preferably formed in one piece and is provided withapertures 18 through which suitable bolts, not shown, may pass in orderto secure the rheostat to a panel or instrument board.

The operating shaft 13 passes through and is rotatably mounted in aheaded metallic bushing 19, held in place in an aperture 20 by a nut 21.The shaft 13 is prevented from longitudinal movement through the bushing19 by a split ring 22 in engagement with the bushing. One end of theshaft 13 contains a central indentation and a transverse slot 23. Asshown more clearly in Fig. 3, an aperture 24 in the contact arm 14 is ofa size and shape such that the contact arm may be pushed over the end ofthe shaft 13 co-operating with the slot 23 and after assembling, the endof the shaft 13 is peened over, thus holding the contact arm 14 securelyto the end of the operating shaft. The contact arm 14 has integraltherewith small projections 25 and by the engaging of these projectionswith the enlarged end of the terminal 17, as shown in Fig. 2, anefficient wiping contact is obtained. The terminal 17 is secured to thebase by means of a rivet 26.

The base member 10 is substantially circular in form but contains anindentation or groove 28 of predetermined length in its peripheryextending, as shown, around apold thelow resistance element 12.

The high resistance element 11. comprises an insulating stri or core 29'about which is wound a high resistance conductor30. The high resistanceelement is of substantially circular sha e and of a width slightlygreater than the wi th ofthe periphery of the base ll). The lowresistance element 12 comprises an insulating strip 31 about which iswound a low. resistance conductor 32. The strips 29 and 31 arepreferably made of a phe olic condensation product or some other suit leinsulating-material. While I have shown the low resistance conductor 32as being made of a wire larger than'the wire forming the high resistancewinding 30, I do'not wishto be limited to this particular arrangementsince the resistancelelement may take other forms. For-instance,theresist'ance element 12 might be wound with the same size or evensmaller wire than the resistance element 11 depending on the efiectiveresistance desired. The high resistance element 11 may be woundeitherwith bare wire or withinsulated wire. If insulated wire is used,the inside and the exposed edge of the element 11' should be cleaned ofthe insulation. The low resistance element 12 is preferably wound withbare wire.

The metallic terminals 15 and 16 are .L-' shaped and one end of eachterminal is cutas shown in Fig. 3, forming two projections 33 and 34,The projection. 33 contains a small hole into which the end of the highresistance conductor 30. is placed and preferably soldered. Stop members36 integral with the terminal 17 act t'o'stop or limit the angularmovement of the contact arm 14. One end of the terminal 17 is enlargedand contains an a erture 37 through which the shaft 13 passes,

t e enlar ed end of the terminal serving as a hearing or the projections25 on the contact arm as described hereinbefore. The outer ends oftheterminals 15, 16 and 17 are cut and bent as shown in Fig. 3 tofacilitate the solderin thereto of external connections.

In or er to secure the various parts of my device in position a metallicclamping member 38, substantially circular in she and containingextensions 39 and 40, 1s provided.

The extensions39 and 40 contain apertures.

through which a bolt 41 is placed and by screwlng this bolt into a nut42 the member 38 is clamped securely around the high resistance. element11, thus holding the low resistance element 12 in the groove 28 betweenthe high resistance element 11 and the base 10. A flexible insulatingstrip 43 of approximately the same width as the clamping memher 38 isadapted to be placed between the clamping member 38 and the highresistance element 11.

In assembling the parts of my rheostat the resistance element 11 isplaced around the eri hery of'the base member thus holding the owresistance element 12 inplace. The termmals 15 and 16 will be clampedbetween the high resistance element -11 and the base- 10in grooves 44 inthe base 10 provided for them. The insulatin strip 43- 'and clampingmember 38 are then p aced around the outside of the hi h resistanceelement 11 and by means of t 6 bolt 41 the resistance elements 11 and 12and the'terminals 15 and 16 are thus securel clampedin place. Theprojections 33 an 34 at the ends of the terminals 15 and 16 are then.bent upwardl at right an-' gles against the right-hand sur ace of thebase I 10 as viewed in Fig. 2.

It will be observed that the winding32 of the low resistance element 12is held,

throughout the, length of the low resistance element, in parallel,electrically contacting relation with the inside of a proximatelyonethird of .the winding 30 orming the high resistance element 11, thebare surfaces of the two windings being pressed against each other dueto theclampmg action of the ring.

38. The-groove 28.is of a width such that, when the resistance elementsare in position, the outer edge of element 12'will be spaced inwardly cmthe contact-making edge of the element 11, that is, the low re 4sistance element 12 will not be engaged by the contact arm 14 as thisarm moves over and in contact with the high resistance element 11.-

Assuming that the contact arm 14 is moved from starting position at a.uniform rate in a counter-clockwise direction, as viewing Fig. 1, theeffective resistance between terminal 16 and terminal 17 will increaseuniformly at a certain rate until the end of the contact arm passes thepoint at which the upper end of the low resistance element 12 engagesthe high resistance element 11. From this point the resistance will alsoincrease uniformly but at a higher rate. This is due. to the fact thatthe two resistance elements are in parallelthroughout the length of thelow resistance element 12 and the effective resistance will thus belower than the resistance of the high resistance element alone.

- While I have shown my current regulating device with terminals at eachend of the resistance so that the device may be used as apotentiometer,'the device may obviously be used as a rheostat by makingconnections only; to the terminals 16 and 17.

rtain features of the specific embodiment of my invention disclosed aredescribed and claimed in a co nding application of Donald R. De Tar,erial No. 294,277, filed July 20, 1928, and assigned to the sameasas asthis invention.

. e I have described my' invention as embodied in concrete form andoperatingin a specific manner in accordance with the provisions of thepatent statutes, it should be understood that I do not limit myinvention thereto since, various modifications thereof will suggestthemselves to those skilled in the art without departing from the spiritof my invention, the scope of which is set forth in the annexed claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is l. A rheostat comprising a main resistance element, a movablecontact member cooperating therewith, and an auxiliary resistanceelement electrically connected substantially throughout its length inparallel with a portion of said main resistance element so as to varythe-ratio of the change of resistance upon corresponding movement ofsaid contact member over the different portions of said main resistanceelement.

2. A current regulating device comprising a plurality of resistanceelements having different resistances per linear unit, means for holdingone of said resistance elements substantially throughout its length inparallel, electrically contacting relation with a portion of the other,and means for including the different portions of said other resistanceelement in a circuit.

3. A rheostat comprising a pair of resistance elements, each of saidelements comprising an insulating support and a resistance conductorwound on said support, means for holding one of said resistance elementssubstantially throughout its length in longitudinal electricalcontacting engagement with a portion of the other, and means forprogressively including the different portions of said other resistanceelement in a circuit.

4. A rheostat comprising a pair of resistance elements, each of saidelements comprising an insulating support and a bare wire resistanceconductor wound on said sup port, means for holding one of saidresistance elements substantially throughout its length in longitudinalengagement with a portion of the other so as to bring the turns of thetwo-elements in electrical conducting relation, and means forprogressively including the different portions of said other resistanceelement in a circuit.

5. A current regulating device comprising an insulating base, a. highresistance element mounted on said base, a movable contact membercooperating therewith, and a low resistance element mounted in contactsubstantially throughout its length in parallel, electrically contactingrelation with a portion of said first mentioned clement so as to varythe ratio of change of resistance upon movement of said contact memberover the difi'e'rent portions of said high resistance element.

6.. A current regulating device comprising an insulating base, anannular resistance element mounted on said base, a contact in slidingengagement with said annular resistance element, and a second resistanceelement of lower resistance than said annular element secured in contactsubstantially throughout its length in parallel, electrically contactingrelation with a portion of said annular resistance element so as to varythe ratio of change of resistance upon movement of said rotating contactover the difierent portions of said annular resistance element.

7. A current regulating device comprising an insulating strip, aresistance conductor wound on said strip, a movable contact membercooperating with said conductor, a second insulating strip, a secondresistance con-- ductor wound on said second strip,said secondresistance conductor being of different resistance than said firstmentioned conductor, and means for securing said second conductor inparallel, electrically ccntaeting relation with a portion of said firstconductor, so as to vary the ratio 01": change of resistance to movementof said contact member.

8. A rheostat comprising a substantially circular insulating base, anannular insulating strip, a high resistance conductor wound on saidstrip, an arc-shaped insulating strip, a low resistance conductor woundon said arc-shaped strip, means for securing said low resistanceconductor throughout its length to said high resistance conductor inparallel, electrically contacting relation therewith, and a movablecontact arm for making con tact with said high resistance conductor.

9. A current regulating device comprising a pair of resistance elements,one being held in overlapping contacting relation with a portion of theother to reduce the eiiective resistance per linear unit of theoverlapped portion thereof, and means for including the diiierentportions of said other resistance element in a. circuit.

10. A current regulating device comprising a resistance element having asubstantially constant resist-ance per linear unit, a movable contactfor progressively including different portions thereof in a circuit, anda. second resistance element held in parallel, electrically contactingrelation with one portion of the first element for varying the ctfectiveresistance per linear unit of portion.

In witness whereof, I have here n my hand this 19th day of July, 1928.

WILLIAM L. BONE").

